This invention relates to improved methods and apparatus for handling saw logs and the like in a sawmill, and more particularly relates to improved methods and apparatus for receiving and transferring saw logs to the deck of the carriage assembly.
It is well known that trees are harvested for the purpose of providing either lumber or wood pulp, and that a debarked and delimbed tree will provide either a so-called "sawlog" to be cut into lumber, or a "chip log" to be cut into chips. Commercial lumber must be of a certain minimum size and length and cannot have any significant defects. Accordingly, only the straighter and longer logs of a minimum diameter can be converted into lumber. Nevertheless, the demand for lumber often exceeds the supply of good saw logs, and thus there is need to produce lumber from logs of less than perfect configuration.
This need to utilize crooked, curved and otherwise less than perfect logs as a source of lumber is, however, conterbalanced by the fact that modern sawmills are designed to operate with a minimum amount of manual labor. Accordingly, such mills incorporate extensive conveyor and transfer devices for the purpose of receiving, stacking, loading and unloading, and conducting the logs from point to point throughout the sawmill. Even the most perfect sawlog is a relatively clumsy article because of its inherently tapered configuration, and when the log is either crooked, curved, or has flattened portions along its surface, such a log can be almost diabolical in its tendency to resist being moved in a preselected direction by mechanical means. Nevertheless, the need to accept these irregular logs has forced sawyers to tolerate frequent and costly interruptions in their operations which result when such a log shifts traversely to its intended course and causes the traditional log jam in the operation.
Th seriousness of this problem cannot be fully appreciated from a consideration of economic factors alone. A juxtaposed sawlog not only restricts production by requiring the operation to be shut down until the stoppage is cleared; it also creates a very real danger to personnel since it usually can be dislodged and properly repositioned only by hand. Furthermore, the problem has been compounded in recent uyears by the very fact that modern sawmills are now almost fully automated, and thus there are now many more points in the operation for such stoppages to occur.
The exigencies of the situation have been met by the installation and use of special remotely controlled manipulating equipment at all of these various points in the operation, whereby a misaligned sawlog may be repositioned before it becomes wedged to cause a stoppage. Although these devices have often been effective to minimize or eliminate stoppage of the operation at many locations throughout the mill, no really satisfactory device or other solution to this problem has ever been available to handle an irregular sawlog at the place at where manipulation of the log has always been a problem, i.e., at the point where the log is loaded onto the carriage which conveys it to the cutting blade.
As is more fully explained in U.S. Pat. No. 3,566,933, the conventional sawmill carriage is a flat bedded conveyance usually mounted on rails leading past a revolving circular saw blade and having two or more "knee assemblies" slidably positioned across its bed. Each of these knee assemblies is provided with a pair of dogs so that, when a saw log is dropped or rolled onto the bed of the carriage in alignment with the rails, it abuts one side of these knee assemblies and is gripped by the dogs, so that it can be held secure and immobile while being carried into the saw blade.
Although the position of the knee assemblies can be shifted traversely across the width of the carriage, it will be readily apparent that when a saw log is deposited onto the carriage it may not, and in fact often does not, align itself into proper abutting relationship to the knee assemblies whereby it can be properly and securely engaged by the dogs. Accordingly, a positioning device commonly referred to as a slapper bar is employed behind the saw log to drive it against the edges or "faces" of the knee assemblies.
As also explained in the aforementioned U.S. Pat. No. 3,566,933, a saw log is first cut on four sides to give it a rectangular configuration, before it is cut into lumber. This requires four separate trips to the saw blade, and also rotation of the log after each cut, since the position turning the saw blade is fixed vis-a-vis the carriage. Although turnin the saw log was historically a manual operation at this point, many devices have been adopted over the years to perform this function mechanically, and most of these devices operate quite satisfactorily with logs of traditional configuration.
The problem to which the present invention is directed arises primarily from the fact that acceptance of logs of more irregular configuration for lumbering purposes has required that the log be further manipulated after being deposited onto the carriage so that its best surface may be presented to the knee assemblies. Often the sawyer is required to turn the log several complete revolutions before this surface can be discovered, and since the log is irregular, each turn creates a tendency for the log to become misaligned and even to roll off the carriage. Thus, the sawyer is required to continually use the slapper bar to return the log to the knees each time it is revolved, and this in turn makes the task more complex for the sawyer. Furthermore, an irregular saw log must often be held jammed up against the knee assemblies to properly secure the dogs, and thus there is often a need with irregular logs to jam the log against the knees with the slapper bar simultaneously with rotation of the log to discover and present its most advantageous side to the dogs. For this reason, there has long been a need for a suitable device which incorporates both the log turner and the slapper bar, and this need has merely been intensified by the present need to accept more irregular logs as a source of lumber.
There have been many attempts to provide a solution to this problem, but all such attempts have been either partially or wholly unsatisfactory for various reasons. In U.S. Pat. No. 189,379 (Orm), a combination slapper bar was proposed which also incorporated teeth for engaging and turning the log. In this device, however, the teeth were exposed at all times, and thus when the bar was slapped against a log with only moderate force, the teeth would either be broken or would be imbedded in the surface of the log.
In the U.S. Pat. No. 1,679,445 (Peaver), a combination log turner and slapper bar is disclosed wherein the teeth are movable within the slapper bar. In this instance, however, the teeth are not retractable, and thus this assembly suffers from the same disadvantages as have hereinbefore been set out with respect to U.S. Pat. No. 189,379.
Other similar devices are disclosed in U.S. Pat. Nos. 300,405 (Stetson), 337,705 (Rodgers), 379,086 (Torrent), 463,334 (Lange), 514,463 (Hill), 559,429 (Wilkins), 2,100,115 (Ward), 2,728,362 (Richardson), and 2,857,941 (Baker). Each of these devices suffers from the same disadvantage, or else it is incapable of being used as either an effective slapper bar or a useful log turner. On the other hand, all of these and other disadvantages of the prior art are overcome with the present invention, and novel means and methods are provided herewith for manipulating a log both rotationally and laterally at the same time.